The MacBook Air laptop is shipped with the battery fully charged. It's usually arrives at your house around 85-95% charge due to charge leakage (nothing to worry about). You don't have to fully drain your battery prior to charging however you should aim to have at least one cycle per month (drop to < 5% then charge to 100%) to maximise your battery life.

you should go for low discharge batteries. Mouse and keyboard are like remote controls, low power but long time. With regular rechargeable batteries, they will get empty every other week (since the battery gets depleted even if you don't use it)
With low discharge batteries (such as Eneloop), the battery keeps it's charge when the mouse enter sleep mode, making it last for months.

The charger detects when the batteries are full and stops.
The maximum charge time is 4.5hours if the batteries are empty.
If the two batteries are at different charge levels when they are inserted, each battery is finished separately. The indicator will indicate done when both batteries are finished.

This could be due to multiple reasons:
1) The batteries are faulty one way or another, are you charging the official Apple ones?
2) The charger is defective.
3) If the light is still orange then the batteries just plain aren't fully charged yet. Leave them in over night and if any light at all in on come morning, you'll know that option 1 or 2 is the answer. I say this because once the batteries charge, the light will turn green, but then the light will turn off completely eventually.

Well, I took an Apple Magic Mouse back to the Apple Centre because after I replaced the batteries, it kept loosing its connection. The guy at the Apple centre told me that Enegizer batteries are actually minutely larger than many other AA batteries - a matter of a fraction of a millimetre, but it counts. He actually held two batteries up to demonstrate it. This indeed causes other batteries to loose contact which makes the connection drop out. Regardless, he replaced that particular Magic Mouse, as a gesture of good faith, but I have subsequently found that if I use any batteries *other* than Energizer in the new one he gave me, the Bluetooth connection to the mouse keeps dropping out.

I have 2200 Energizer batteries (that were charged by a pure garbage 15-min Energizer recharger) in my Magic Mouse. When fully charged and cooled down 3 hrs later, the percentage starts from approx. 72%, not 100%. Do Apple's batteries start out at less than 100%? One reviewer mentioned the BT keyboard started at 81%.

I have a Mighty Mouse (not a Magic Mouse). Even with fully-charged NiMH batteries, the charge percentage never shows more than about 70-75%. Same with the wireless keyboard.

The battery charge display is calibrated for alkaline batteries, not NiMH. Alkaline batteries start at 1.5V and the voltage drops relatively quickly as they discharge. NiMH batteries start at 1.2V, and the voltage stays pretty constant until they are nearly discharged. Software that's calibrated to show the remaining charge in an alkaline battery won't show the charge accurately for NiMH batteries. Any brand of battery will behave this way. It doesn't indicate a problem with the batteries; they are just different than alkaline.

Maybe Apple will update the software so it can show the charge more accurately for NiMH batteries.

All NiCD and NiMH batteries (including these) are "nominally" 1.2V (but can reach 1.45-1.6V fresh off the charger). Most disposable batteries are 1.5-1.6V when new but are down to 1.2V around when they're halfway used at moderate power drain, and earlier for high-drain devices. Any device that will not work down to 1V (per battery) isn't giving you your money's worth out of alkalines. Lithium AAs are different yet again, running 1.6-1.7V, which can be good or bad depending on the device (it'll burn out incandescent flashlight bulbs early).